Help with Linker error, while using multiple inheritance

Hi
I have been trying to compile this code, in this I had a class clocktype with its header and implementation file and now I have to extend this class to be able to implement the function timezone in it. This is a program where I have to use two header files in my derived class.
I am posting my code here:

Code:

//header file clocktype
#ifndef h_clocktype
#define h_clocktype
#include<string>
using namespace std;


class clocktype
{
public:
	void settime(int hours, int minutes, int seconds);
	void gettime(int& hours, int& minutes, int& seconds);
	void printtime();
	void incseconds();
	void incminutes();
	void inchours();

	clocktype (int hours, int minutes, int seconds);
	clocktype();

protected:
	int hr;
	int min;
	int sec;
};
#endif

// implemnetation file
#include<iostream>
#include<conio.h>
#include "clocktype.h"

using namespace std;

void clocktype::settime(int hours, int minutes, int seconds)
{
	if(0<= hours && hours<24)
		hr=hours;
	else
	hr=0;

	if(0<=minutes && minutes<60)
		min=minutes;
	else
		min=0;

	if (0<=seconds && seconds<60)
		sec=seconds;
	else
		sec=0;
}
void clocktype::gettime(int& hours, int& minutes, int& seconds)
{
	hours=hr;
	minutes=min;
	seconds=sec;
}

void clocktype::printtime()
{
	if(hr<10)
		cout<<"0";
		cout<<hr<<":";
	if(min<10)
		cout<<"0";
	cout<<min<<":";
	if(sec<10)
		cout<<"0";
	cout<<sec;
}

void clocktype::inchours()
{
	hr++;
	if(hr<23)
		hr=0;
}
void clocktype::incminutes()
{
	min++;
	if(min<59)
		min=0;
	inchours();
}
void clocktype::incseconds()
{
	sec++;
	if(sec<59)
		sec=0;
	incminutes();
}

clocktype::clocktype()
{
	hr=0;
	min=0;
	sec=0;
}
clocktype::clocktype(int hours, int minutes, int seconds)
{
	if(0<= hours && hours<24)
		hr=hours;
	else
	hr=0;

	if(0<=minutes && minutes<60)
		min=minutes;
	else
		min=0;

	if (0<=seconds && seconds<60)
		sec=seconds;
	else
		sec=0;
}

// main function

int main()
{
	clocktype myclock;
	myclock.settime( 12, 14, 40);
	cout<<" The time now is : ";
		myclock.printtime();
	myclock.settime( 24, 60, 60);
	cout<<"\n The time now is : ";
	myclock.printtime();

	getch();
}

And now I have the derived class

Code:

#ifndef h_clocktype2
#define h_clocktype2
#include<iostream>
#include"clocktype.h"
using namespace std;

enum zonetype {GMT, EST, PST, IST, CET};
class clocktype2: public clocktype
{
	public:
	void settime(int hours, int minutes, int seconds,zonetype timezone);
	
	void printtime();
	
	clocktype2 (int hours, int minutes, int seconds, zonetype timezone);
	clocktype2();

private:
	zonetype tz;
};
#endif

#include<iostream>
#include<conio.h>
#include"clocktype.h"
#include"clocktype2.h"


using namespace std;

void clocktype2::settime(int hours, int minutes, int seconds, zonetype timezone)
{
	hours=hr;
	minutes=min;
	seconds=sec;
	timezone=tz;

}
void clocktype2::printtime()
{
	switch(tz)
	{
	case GMT:
		cout<<"GMT";
		break;
	case EST:
		cout<<"EST";
		break;
	case PST:
		cout<<"PST";
		break;
	case IST:
		cout<<"IST";
		break;
	case CET:
		cout<<"CET";
		break;
	}
}
clocktype2::clocktype2(){
hr=0;
	min=0;
	sec=0;
	tz=GMT;
		   }

clocktype2::clocktype2(int hours, int minutes, int seconds, zonetype timezone)
{
hours=hr;
	minutes=min;
	seconds=sec;
	timezone=tz;
}

int main()
{
	clocktype2 clock;
	clock.settime( 12, 14, 40, GMT);
	cout<<" The time now is : ";
		clock.printtime();
	clock.settime( 24, 60, 60, IST);
	cout<<"\n The time now is : ";
	clock.printtime();

	getch();
}

Now when I try to run this program it gives me the following error:
------ Build started: Project: lab-4, Configuration: Debug Win32 ------
Linking...
clocktypeimp2.obj : error LNK2019: unresolved external symbol "public: __thiscall clocktype::clocktype(void)" (??0clocktype@@QAE@XZ) referenced in function "public: __thiscall clocktype2::clocktype2(void)" (??0clocktype2@@QAE@XZ)
C:\Documents and Settings\user\My Documents\Visual Studio 2008\Projects\lab-4\Debug\lab-4.exe : fatal error LNK1120: 1 unresolved externals
Build log was saved at "file://c:\Documents and Settings\user\My Documents\Visual Studio 2008\Projects\lab-4\lab-4\Debug\BuildLog.htm"
lab-4 - 2 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

That is inheritance, not multiple inheritance. In multiple inheritance a derived class inherits from multiple base classes.

As to your error, there's nothing wrong with your code. You have a linker error, probably because you didn't correctly add clocktype to your lab-4 project. It's not enough to just #include the clocktype header. You have to add clocktype to your build configuration so that the clocktype implementation is compiled along with the clocktype2 implementation.

Oh Thanks for the correction.
But all my files are in the same project, Lab-4. And still it is giving me this Linker error. I can not figure out why ?
Do I have to add #ifndef and #define and #endif to my .cpp file of my base class?

Originally Posted by Lichi

Do I have to add #ifndef and #define and #endif to my .cpp file of my base class?

It has nothing to do with header guards. There's something wrong with the way your project is configured. I can't help you there -- I'm a complete novice when it comes to MS Visual Studio, but I can tell you that I just pasted your exact code into a new project (actually the first project that I have ever created with VS2010Express), setting up 5 files: clocks.cpp (for the main function), clocktype.h, clocktype.cpp, clocktype2.h and clocktype2.cpp, and it builds and runs without errors (after I figured out how to set it to NOT use precompiled headers).

I suggest that you try removing the clocktype and clocktype2 headers and implementation files from your project directory, then go to Project/Add Item/C++ File and Project/Add Item/Header File and create new files and then paste your code into those files.

Oh I just wanted to tell, that my program worked yesterday. And the error I was having was so Silly, I had two mains in my program I did not delete the main from the base class.
Thanks alot